Thanks for the review, SKY.
The overclocking results for the 3rd party 670s should be interesting: do you get better OC from longer cards (e.g. Gigabyte) because the components are more spaced out for cooling, or worse OC results because some of the traces would be longer? When that review comes out I'll definitely jump straight to those results of short PCB vs longer PCB.

I'm still waiting for a "midrange" card from this lineup that will go against the Radeon 7850 (somehow I'm gaming on my backup 7900GS!), although seeing this review and the 680's review, it should be another slaughter when that card comes out.

Overclocking is so different with these cards that you almost have to throw preconceptions out the window. Since the overclocks are based upon Boost speeds, if you give the ASIC excess TDP headroom (in other words, getting it to run cooler) it will Boost higher based upon your increased offset. As such, any card with an upgraded cooling assembly will naturally achieve higher clock speeds than a reference design. This isn't due to PCB traces or even component selection as those items will only come into effect when you are pushing the upper limits of the architecture through exotic means of cooling.

Considering the performance of the GTX 670, I'd predict that any GTX 660 would match or potentially beat the HD 7950. I think you would have to go downmarket in NVIDIA's lineup (ie: potential GT 650) for a card that would compete with the HD 7870 and HD 7850.